The present invention relates generally to printers, and, more specifically, to replaceable printer rolls therein.
A typical printer includes a roll of printing paper upon which any desirable information may be printed. The paper is wound in a continuous sheet on a supporting core, and the core is mounted on a driven spindle in the printer. In a thermal printer, the core includes thermal transfer ribbon wound thereon which is thermally activated during printing.
When the paper is depleted on the core, the empty core is removed from the spindle and replaced with a fully wound core for returning the printer to service.
The core typically includes retaining features for accurately retaining the core axially on the spindle in proper alignment with the printing mechanism, and circumferentially retaining the core around the spindle for rotating therewith as the spindle is driven during printer operation.
In one conventional design, the spindle includes three axial slots around the perimeter thereof which axially receive corresponding straight axial ribs projecting inwardly along the inner surface or bore of the core. The core may be easily inserted axially over the spindle by engaging the corresponding ribs and slots, with the ribs providing circumferential retention around the spindle for being driven in rotation therewith.
However, additional features are required for locking the core in axial position over the spindle and preventing its unintended liberation therefrom or misalignment thereon. This increases the complexity of the core and spindle assembly, and correspondingly increases the cost thereof.
Cost is a significant factor in the manufacture and use of printer rolls and must be minimized for maintaining competitive advantage in the market for supplying replacement printing rolls.
Accordingly, it is desired to provide an improved core for winding sheet rolls thereon having corresponding retention features for being mounted to a supporting spindle.
A core includes a tubular body for supporting a wound sheet roll on a spindle. The body includes an annular outer surface for receiving the sheet roll, and an annular inner surface defining a bore for receiving the spindle. A plurality of ribs project inwardly from the body inner surface and extend axially between opposite first and second openings for nesting in the corresponding slots in the spindle. At least one of the ribs includes a bowed side surface in the exemplary form of a fork for frictionally engaging a corresponding one of the spindle slots to frictionally retain the core axially thereon.